Sheet detection device and image forming apparatus

Abstract

The invention discloses a sheet detection device and an image forming apparatus. The sheet detecting apparatus includes: a measuring unit configured to measure a characteristic quantity of a sheet conveyed by a conveying unit; a pressing member movable between a first position separated from the measuring unit and a second position closer to the measuring unit than the first position; and a moving unit configured to move the pressing member, in a case where the sheet has not been conveyed to the measurement position of the measurement unit by the conveying unit, the pressing member is arranged in a first position by the moving unit, in a case where the sheet has been conveyed to the measurement position of the measurement unit by the conveying unit, and in a case where the sheet has been conveyed to the measurement position of the measurement unit by the conveying unit, the pressing member is arranged in a second position by the moving unit. The pressing member is moved from the first position to the second position.

Description

Technical Field

[0001] The present disclosure relates to a sheet detection device including a media sensor for discriminating a sheet type and an image forming apparatus including the sheet detection device. Background Art

[0002] In recent years, an image forming apparatus includes a media sensor for discriminating the type of a sheet as a recording medium. The media sensor measures a feature amount of a sheet by using, for example, an optical sensor or an ultrasonic sensor. The image forming apparatus extracts relevant sheet information from pre-registered sheet information based on the measurement result of the feature amount of the sheet obtained by the media sensor, and discriminates the type of the sheet. The sheet information is information including feature amounts (e.g., basis weight and surface properties) of each type of sheet.

[0003] The media sensor measures the characteristic quantity from the sheet being conveyed. In this case, the distance between the media sensor and the sheet may change due to the positional variation (swing) of the sheet at the measuring position of the media sensor. The swing of the sheet may reduce the detection accuracy of the characteristic quantity by the media sensor. In particular, in the case where the media sensor is an optical sensor, the sheet may deviate from the focus of the optical sensor, thereby reducing the accuracy of the measurement result. This may result in a reduction in the accuracy of distinguishing the type of sheet.

[0004] On the other hand, Japanese Patent Laid-Open No. 2018-200478 discloses a configuration in which a roller serving as a pressing member is arranged at a position facing a media sensor across a conveying path of a sheet. In this configuration, the sheet is pressed against the surface of the media sensor by the roller to suppress the swing of the sheet. U.S. Patent No. 10,894,689 discloses a configuration in which a roller is arranged so as not to contact a member facing the roller in a direction perpendicular to the sheet surface.

[0005] However, although the pressing member that presses the sheet against the media sensor suppresses the reduction in sheet detection accuracy, the pressing of the sheet may cause sheet conveying failures such as paper jams, etc. The present disclosure is made in view of the above problems, and a main object of the present disclosure is to provide a sheet detection device that can suppress the reduction in sheet detection accuracy and also suppress the occurrence of sheet conveying failures. Summary of the invention

[0006] According to an embodiment of the present disclosure, a sheet detection device includes: a measuring component for measuring a feature amount of a sheet conveyed by a conveying component; a pressing member capable of moving between a first position separated from the measuring component and a second position closer to the measuring component than the first position; and a moving component configured to move the pressing member, wherein the pressing member is arranged at the first position by the moving component when the sheet has not yet been conveyed by the conveying component to the measuring position of the measuring component, wherein the moving component is configured to move the pressing member from the first position to the second position when the sheet has been conveyed by the conveying component to the measuring position of the measuring component, and wherein the measuring component is configured to measure the feature amount of the sheet in a state where the pressing member is arranged at the second position.

[0007] According to another embodiment of the present disclosure, a sheet detection device includes: a measuring component for measuring a characteristic amount of a sheet conveyed by a conveying component; a pressing member capable of moving between a first position separated from the measuring component and a second position closer to the measuring component than the first position; and a moving component configured to move the pressing member, wherein, in a case where the sheet has not been conveyed by the conveying component to the measuring position of the measuring component, the pressing member is arranged at the first position by the moving component, and wherein, in a case where the sheet has been conveyed by the conveying component to the measuring position of the measuring component, the pressing member that has been moved from the first position to the second position by the moving component is arranged at the second position until the sheet passes through the measuring position.

[0008] According to another embodiment of the present disclosure, a sheet detection device includes: a measuring component for measuring a characteristic amount of a sheet conveyed by a conveying component; a pressing member capable of moving between a first position separated from the measuring component and a second position closer to the measuring component than the first position; and a moving component configured to move the pressing member, wherein the moving component is configured to move the pressing member from the first position to the second position in a state where an initial adjustment of the measuring component is performed in a state where the sheet has not yet been conveyed to the measuring position of the measuring component, wherein the measuring component is configured to perform the initial adjustment in a state where the pressing member is arranged in the second position, and wherein the moving component is configured to move the pressing member from the second position to the first position after performing the initial adjustment.

[0009] According to another embodiment of the present disclosure, a sheet detection device includes: a measuring component for measuring a characteristic amount of a sheet conveyed by a conveying component; a pressing member capable of moving between a first position separated from the measuring component and a second position closer to the measuring component than the first position; and a moving component configured to move the pressing member, wherein the moving component is configured to move the pressing member from the first position to the second position in a state where an initial adjustment of the measuring component is performed in a state where the sheet has not yet been conveyed to the measuring position of the measuring component, wherein the measuring component is configured to perform the initial adjustment in a state where the pressing member is arranged in the second position, and wherein the moving component is configured to move the pressing member from the second position to the first position after performing the initial adjustment.

[0010] According to still another embodiment of the present disclosure, an image forming apparatus includes a sheet detection device, the sheet detection device including: a measuring part for measuring a feature amount of a sheet conveyed by a conveying part; a pressing member capable of moving between a first position separated from the measuring part and a second position closer to the measuring part than the first position; and a moving part configured to move the pressing member, wherein the pressing member is arranged at the first position by the moving part when the sheet has not been conveyed by the conveying part to the measuring position of the measuring part, wherein the moving part is configured to move the pressing member from the first position to the second position when the sheet has been conveyed by the conveying part to the measuring position of the measuring part, and wherein the measuring part is configured to measure the feature amount of the sheet in a state where the pressing member is arranged at the second position; and an image forming part configured to form an image by using an image forming condition based on the feature amount of the sheet measured by the measuring part.

[0011] According to still another embodiment of the present disclosure, an image forming apparatus includes a sheet detection device, the sheet detection device including: a measuring part for measuring a feature amount of a sheet conveyed by a conveying part; a pressing member capable of moving between a first position separated from the measuring part and a second position closer to the measuring part than the first position; and a moving part configured to move the pressing member, wherein, in a case where the sheet has not been conveyed by the conveying part to a measuring position of the measuring part, the pressing member is arranged at the first position by the moving part, and wherein, in a case where the sheet has been conveyed by the conveying part to the measuring position of the measuring part, the pressing member that has been moved from the first position to the second position by the moving part is arranged at the second position until the sheet passes through the measuring position; and an image forming part configured to form an image by using an image forming condition based on the feature amount of the sheet measured by the measuring part.

[0012] According to still another embodiment of the present disclosure, an image forming apparatus includes a sheet detection device, the sheet detection device including: a measuring part for measuring a characteristic amount of a sheet conveyed by a conveying part; a pressing member capable of moving between a first position separated from the measuring part and a second position closer to the measuring part than the first position; and a moving part configured to move the pressing member, wherein the moving part is configured to move the pressing member from the first position to the second position in a case where an initial adjustment of the measuring part is performed in a state where the sheet has not yet been conveyed to the measuring position of the measuring part, wherein the measuring part is configured to perform the initial adjustment in a state where the pressing member is arranged in the second position, and wherein the moving part is configured to move the pressing member from the second position to the first position after performing the initial adjustment; and an image forming part configured to form an image by using an image forming condition based on the characteristic amount of the sheet measured by the measuring part.

[0013] According to still another embodiment of the present disclosure, an image forming apparatus includes a sheet detection device, the sheet detection device including: a measuring part for measuring a characteristic amount of a sheet conveyed by a conveying part; a pressing member capable of moving between a first position separated from the measuring part and a second position closer to the measuring part than the first position; and a moving part configured to move the pressing member, wherein the moving part is configured to move the pressing member from the first position to the second position in a case where an initial adjustment of the measuring part is performed in a state where the sheet has not yet been conveyed to the measuring position of the measuring part, wherein the measuring part is configured to perform the initial adjustment in a state where the pressing member is arranged in the second position, and wherein the moving part is configured to move the pressing member from the second position to the first position after performing the initial adjustment; and an image forming part configured to form an image by using an image forming condition based on the characteristic amount of the sheet measured by the measuring part.

[0014] Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings). BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a configuration diagram of an image forming apparatus.

[0016] Figure 2A and Figure 2B It is an enlarged view of the fixing unit.

[0017] Figure 3 This is a diagram illustrating the controller.

[0018] Figure 4 This is a diagram illustrating the configuration of the media sensors.

[0019] Figure 5 This is a diagram illustrating the configuration of the media sensors.

[0020] Fig. 6A and Figure 6B This is a diagram illustrating the reading results obtained by the optical sensor.

[0021] Figure 7 It is a configuration diagram of the moving mechanism.

[0022] Fig. 8A and Figure 8B This is a diagram for explaining the operation of the moving mechanism.

[0023] Fig. 9 This is a diagram showing the arrangement of the rollers facing the media sensor.

[0024] Fig. 10A and Fig. 10BEach of them is an explanatory diagram of the function of the roller facing the media sensor.

[0025] Fig.11 is a process flow chart for illustrating the movement process of the roller facing the media sensor.

[0026] Fig. 12A , Fig. 12B and Fig. 12C It is an explanatory diagram of the operation during the movement process of the roller facing the media sensor.

[0027] Fig.13 is a process flow chart for illustrating a process of cleaning the optical sensor surface.

[0028] Fig.14 This is a diagram illustrating the configuration of the media sensors. DETAILED DESCRIPTION

[0029] Now, a description is given of at least one exemplary embodiment of the present disclosure with reference to the accompanying drawings. In the following description, "basis weight" is the mass per unit area of ​​a sheet and is expressed in g / m^2 units.

[0030] <Image Forming Apparatus>

[0031] Figure 1 201 is a configuration diagram of an image forming apparatus according to at least one embodiment. An image forming apparatus 201 according to at least one embodiment is, for example, a laser beam printer of a tandem intermediate transfer type using an electrophotographic process. The image forming apparatus 201 forms a full-color image or a monochrome image on a sheet S as a recording medium based on image data acquired from an external device such as a personal computer via a network or based on image data acquired from an image reading device 202 provided on an upper portion of the image forming apparatus 201, and outputs the sheet S.

[0032] The image forming apparatus 201 has components for forming an image in a main body 201A, and includes an image reading device 202 and an operation unit 502 on the top of the main body 201A. A delivery space D is defined between the main body 201A of the image forming apparatus 201 and the image reading device 202, and the delivery space D includes a placement portion 223 for receiving a sheet S to be delivered thereto after image formation.

[0033] The image reading device 202 is a reader that reads an image from a manuscript to generate image data. The image reading device 202 is used, for example, in a process of copying a manuscript. The image reading device 202 in at least one embodiment is configured as a part of the image forming apparatus 201. However, the image reading device 202 is not limited to this configuration, and the image reading device 202 may be electrically connected to the image forming apparatus 201 as a device different from the image forming apparatus 201.

[0034] The operation unit 502 is a user interface including an input interface and an output interface. Examples of the input interface include various key buttons and a touch panel. Examples of the output interface include a display and a speaker. The user can input various instructions to the image forming device 201 via the operation unit 502. The image forming device 201 notifies the user of various types of information by displaying various screens on the display of the operation unit 502. The operation unit 502 in at least one embodiment is configured as a part of the image forming device 201. The operation unit 502 is not limited to this configuration, and the operation unit 502 can be electrically connected to the image forming device 201 as a device different from the image forming device 201.

[0035] The image forming apparatus 201 includes an image forming unit 201B, an intermediate transfer unit 201C, a secondary transfer unit 201D, a fixing device 201E, and a cassette sheet feeding unit 230 in a main body 201A. The main body 201A includes a manual sheet feeding unit 235.

[0036] The box sheet feeding units 230 each feed a sheet S from a corresponding sheet feeding box 1 accommodating the sheet S. The box sheet feeding unit 230 includes a pickup roller 2 and a separation unit. The separation unit includes a feed roller 3 and a retard roller 4 for separating the sheet S sent out from the pickup roller 2. The sheet S is fed one by one from the sheet feeding box 1 by the pickup roller 2 and the separation unit. In at least one embodiment, a description of a configuration in which a plurality of (in this example, four) box sheet feeding units 230 are provided is given. However, any number of box sheet feeding units 230 may be provided. The sheet S fed from the box sheet feeding unit 230 is conveyed to the registration roller pair 240 via the conveying roller pair 280 and 290.

[0037] The sheets S may be fed from a unit other than the cassette sheet feeding unit 230, that is, from the manual sheet feeding unit 235. The manual sheet feeding unit 235 includes a manual feeding tray 5 for receiving the sheets S placed by the user. Similar to the cassette sheet feeding unit 230, the manual sheet feeding unit 235 includes a pickup roller and a separation unit, and the sheets S are fed one by one from the manual feeding tray 5. The sheets S fed from the manual sheet feeding unit 235 are also conveyed to the registration roller pair 240 via the conveying roller pair 280 and 290.

[0038] The media sensor 100 for measuring the characteristic amount of the sheet S is arranged on the conveying path between the conveying roller pair 280 and the conveying roller pair 290. The media sensor 100 outputs, for example, information corresponding to the basis weight and information corresponding to the surface property as the characteristic amount of the sheet S conveyed from the cassette sheet feeding unit 230 or the manual sheet feeding unit 235. The media sensor 100 may be arranged at both or at least one of a position where the sheet S fed from the cassette sheet feeding unit 230 can be detected and a position where the sheet S fed from the manual sheet feeding unit 235 can be detected. The configuration details of the media sensor 100 will be described later.

[0039] The image forming unit 201B is a four-drum full-color type, and includes a laser scanner 210 and four process boxes 211. The four process boxes 211 form toner images of four colors (specifically, yellow (Y), magenta (M), cyan (C), and black (K)). Each process box 211 includes a photosensitive drum 212, a charging device 213, and a developing device 214. A toner box 215 is arranged above the process box 211. The toner box 215 replenishes toner to each developing device 214.

[0040] The intermediate transfer unit 201C includes an intermediate transfer belt 216 wound around a driving roller 216a and a tension roller 216b. Inside the intermediate transfer belt 216, four primary transfer rollers 219 are provided, which abut against the intermediate transfer belt 216 at positions opposite to the photosensitive drum 212. The driving roller 216a driven by a driving unit (not shown) rotates the intermediate transfer belt 216 in the direction of the arrow.

[0041] The secondary transfer unit 201D includes a secondary transfer roller 217, which is arranged to sandwich the intermediate transfer belt 216 at a position opposite to the driving roller 216a. The fixing device 201E is arranged on the downstream side of the secondary transfer roller 217 in the conveying direction of the sheet S, and includes a pressure roller 220a and a heating roller 220b. On the downstream side of the fixing device 201E in the conveying direction of the sheet S, a first delivery roller pair 225a, a second delivery roller pair 225b, and a duplex printing reversing unit 201F are arranged. The duplex printing reversing unit 201F includes a reversing roller pair 222 and a re-conveying path R. The reversing roller pair 222 can rotate in the forward and reverse directions. The re-conveying path R allows the sheet S with an image formed on one side to be conveyed to the image forming unit 201B.

[0042] The image forming apparatus 201 configured as described above operates as follows. The image forming apparatus 201 acquires image data together with an instruction to start a print job from the image reading device 202 or from an external device, and forms an image corresponding to the image data on a sheet S. At this time, the image forming apparatus 201 performs each step of image formation based on an operating condition given according to the characteristics of the sheet S.

[0043] A print job is a series of operations performed based on a print signal indicating that an image is to be formed on a sheet S, in which the sheet S is conveyed, an image is formed on the sheet S, and after the image forming operation is completed, the sheet S is delivered to the placement portion 223. The image forming apparatus 201 acquires an instruction to start a print job from the operation unit 502 or an external device.

[0044] The image forming unit 201B uniformly charges the surface of the photosensitive drum 212 to a potential having a predetermined polarity using the charging device 213. The laser scanner 210 irradiates the uniformly charged surface of the photosensitive drum 212 with the corresponding laser beam modulated based on the image data. Thus, electrostatic latent images for the corresponding colors (yellow, magenta, cyan, and black) are formed on the corresponding surfaces of the photosensitive drum 212.

[0045] The image forming unit 201B develops the electrostatic latent image formed on the photosensitive drum 212 using the developing device 214. The electrostatic latent image is developed on the photosensitive drum 212 with the toner of the corresponding color, so that a toner image of the corresponding color is formed on the photosensitive drum 212. The toner image is sequentially transferred from the photosensitive drum 212 to the rotating intermediate transfer belt 216 in an overlapping manner by the primary transfer roller 219. In this way, a full-color toner image is formed on the intermediate transfer belt 216. The intermediate transfer belt 216 rotates to convey the toner image to the secondary transfer unit 201D.

[0046] Simultaneously with such an operation of forming a toner image, the sheets S are conveyed one by one to the registration roller pair 240 by the cassette sheet feeding unit 230 or the manual sheet feeding unit 235. Before the sheets S reach the registration roller pair 240, the characteristic amount of the sheets S is measured by the medium sensor 100. The image forming apparatus 201 sets image forming conditions based on the measured characteristic amounts, and performs subsequent image formation based on the set image forming conditions. The image forming conditions to be set include, for example, the voltage value of the secondary transfer bias applied to the secondary transfer roller 217 during the transfer of the toner image to the sheet S, the fixing temperature when the image is fixed by the fixing device 201E, and the conveying speed of the sheet S at the time of fixing.

[0047] The registration roller pair 240 corrects the skew of the sheet S conveyed to the registration roller pair 240. After the skew is corrected, the sheet S is conveyed to the secondary transfer unit 201D by the registration roller pair 240 in synchronization with the timing at which the toner image carried on the intermediate transfer belt 216 is conveyed to the secondary transfer unit 201D. The secondary transfer unit 201D transfers the full-color toner image from the intermediate transfer belt 216 to the sheet S while applying a secondary transfer bias to the secondary transfer roller 217.

[0048] The sheet S to which the toner image is transferred is conveyed to the fixing device 201E. The fixing device 201E sandwiches the sheet S with a nip portion defined by the pressure roller 220a and the heating roller 220b and conveys the sheet S. The fixing device 201E heats the sheet S with the heating roller 220b while sandwiching and conveying the sheet S, thereby melting and mixing the toners of the respective colors on the sheet S. Furthermore, the fixing device 201E presses the sheet S with the pressure roller 220a, thereby fixing the melted and mixed toners to the sheet S. At this time, the viscosity of the melted toner generates an adhesive force on the sheet S to the heating roller 220b.

[0049] Figure 2A and Figure 2B 201E. In the case where the rigidity (strength) of the sheet S is low, the adhesion force generated on the sheet S to the heating roller 220b may cause the sheet S to be rolled up by the rotating heating roller 220b ( Figure 2B ). Therefore, the separation plate 221 for separating the sheet S is provided on the downstream side of the heating roller 220b in the conveying direction of the sheet S ( Figure 2A ).

[0050] The image forming apparatus 201 can determine the state of the separation plate 221 according to the type and basis weight of the sheet S discriminated from the measurement result of the media sensor 100. For example, in the case where a sheet S of a type having a small rigidity is subjected to image formation, as shown in FIG. Figure 2A As shown, the separation plate 221 is arranged so that the distal end of the separation plate 221 contacts the surface of the heating roller 220b, thereby separating the sheet S from the heating roller 220b. In the case where the sheet S of a type having a large rigidity is subjected to image formation, the sheet S is not rolled up by the heating roller 220b. Therefore, the separation plate 221 is arranged so that the distal end of the separation plate 221 does not contact the surface of the heating roller 220b. In this way, the surface of the heating roller 220b can be prevented from being worn by the separation plate 221.

[0051] The sheet S to which the image is fixed is delivered to the delivery space D by any one of the first delivery roller pair 225a and the second delivery roller pair 225b. The sheet S is placed on the placement portion 223 provided in a protruding manner on the bottom surface of the delivery space D. In the case where images are formed on both sides of the sheet S, the sheet S on which the image is fixed on one side is conveyed to the re-conveying path R by the reversing roller pair 222. The sheet S is conveyed to the image forming unit 201B again, and an image is formed on the other side of the reversed sheet S. The re-conveying path R allows the sheet S to be conveyed to the conveying path between the conveying roller pair 290 and the registration roller pair 240.

[0052] <Control Unit>

[0053] Figure 3 2 is an explanatory diagram of a controller that controls the operation of such an image forming apparatus 201. The controller 200 is, for example, an information processing device including a central processing unit (CPU). The controller 200 can be implemented by, for example, a microprocessor unit (MPU) or an application specific integrated circuit (ASIC). The controller 200 controls the above-mentioned image forming operation performed by the image forming apparatus 201.

[0054] The controller 200 includes a control unit 400 and a memory 401. The memory 401 stores, for example, a control program for an image forming operation, initial values ​​of various setting values, and various types of data required for the image forming operation. In addition, the memory 401 has a storage area for storing a print mode database 402. The print mode database 402 is a database in which the correspondence between sheet characteristics and image forming conditions (printing modes) is pre-set. Examples of sheet characteristics include the type and basis weight of the sheet. The control unit 400 is connected to the operation unit 502, the image reading device 202, the image forming unit 201B, the conveying unit 600, the sensor 601, and the media sensor 100. The control unit 400 can communicate to and from the host device 501 as an external device.

[0055] The host device 501 is, for example, a personal computer, an image scanner, or a fax machine. The operation unit 502 inputs, for example, instructions and settings received via the input interface to the control unit 400. The operation unit 502 outputs various types of information via the output interface under the control of the control unit 400. As described above, the operation unit 502 includes a display as an output interface, and displays various types of information on the display.

[0056] The conveying unit 600 includes a conveying roller pair 280 and 290, a pickup roller 2, a feed roller 3, a retard roller 4, and a motor for driving these rollers. The conveying unit 600 also includes a registration roller pair 240, a secondary transfer roller 217, a pressure roller 220a, a heating roller 220b, and a motor for driving these rollers. In addition, the conveying unit 600 includes a first delivery roller pair 225a, a second delivery roller pair 225b, a reverse roller pair 222, other rollers for conveying the sheet S in the image forming apparatus 201, and a motor for driving these rollers. The conveying unit 600 controls the feeding of the sheet S by driving and controlling the respective motors under the control of the control unit 400.

[0057] The control unit 400 acquires an instruction to start a print job from the host device 501 or the operation unit 502, and starts the print job. The control unit 400 acquires image data from the host device 501 or the image reading device 202, and performs image processing on the acquired image data. The control unit 400 executes the print job by causing the image forming unit 201B to form a toner image based on the image data that has been image processed and causing the conveying unit 600 to feed the sheet S.

[0058] The media sensor 100 includes an information processing unit 160, an ultrasonic sensor 120, and an optical sensor 150. In at least one embodiment, the ultrasonic sensor 120 and the optical sensor 150 are used as a sheet measuring unit. In addition to the ultrasonic sensor 120 and the optical sensor 150, a sheet detection sensor 270 is connected to the information processing unit 160. The information processing unit 160 includes a memory 1601 therein. The information processing unit 160 is an information processing device implemented by, for example, a CPU, an MPU, or an ASIC.

[0059] Image forming conditions (e.g., conveying speed at fixing, target fixing temperature, and transfer voltage at secondary transfer) differ depending on the physical properties (e.g., basis weight, rigidity, surface properties, and material) of the sheet S on which the image is to be formed. Therefore, it is necessary to set the image forming conditions in advance according to the characteristic amount of the sheet S to be used when forming the image.

[0060] Depending on the type of sheet S, there may be some restrictions when setting the sheet S to the feed port (sheet feed cassette 1 or manual feed tray 5). For example, some thick paper sheets with high rigidity can be fed only from the manual feed tray 5 with a conveying path with a small curvature. Coated paper sheets with smooth surface texture and strong adhesion between sheets need to be fed one by one from the manual feed tray 5 to prevent multiple sheets from being conveyed on top of each other. Paper sheets made of pulp as a raw material generally have different bending rigidities in the length and width directions because of the deviation in the orientation direction (fiber orientation) of the pulp fibers that occurs due to the manufacturing method. Therefore, a recommended orientation of the sheet in the length and width directions when setting the sheet to the feed port in a manner that the bending rigidity against the bend in the conveying path becomes smaller is given. In addition, for a single-sided coated paper sheet obtained by coating only one side of a plain paper sheet, the orientation in the up-down direction is specified when setting so that printing is performed on the coated side.

[0061] There are also some types of sheets that cannot be used in the image forming apparatus 201. For example, in the case of a thick paper sheet having too high rigidity, the conveyance of the sheet may be stopped due to the resistance generated when the sheet is conveyed along the curved conveying path. A thin paper sheet having too low rigidity is strongly affected by the adhesion force generated between the melted toner and the heating roller 220b when passing through the fixing device 201E. Therefore, there is a possibility that the sheet cannot be separated from the heating roller 220b by the separation plate 221, but is directly wound around the heating roller 220b ( Figure 2B ). Furthermore, in the case of a synthetic paper sheet made not of pulp but of synthetic resin as a raw material, there is a case where the sheet is melted due to heating in the fixing device 201E, thereby contaminating the heating roller 220b.

[0062] Therefore, in order to appropriately perform image formation, it is important to identify the type of the sheet S to be used based on the feature amount of the sheet S before image formation. Therefore, before the sheet S is conveyed to the secondary transfer unit 201D, the media sensor 100 needs to measure the feature amount of the sheet S. The operation of the media sensor 100 is controlled by the information processing unit 160, and the processing of the respective measurement results of the ultrasonic sensor 120 and the optical sensor 150 is performed by the information processing unit 160. The information processing unit 160 operates under the control of the control unit 400, and transmits the feature amount of the sheet S obtained from the respective measurement results of the ultrasonic sensor 120 and the optical sensor 150 to the control unit 400.

[0063] The control unit 400 and the information processing unit 160 start the sheet measurement sequence based on the detection result obtained by the sheet detection sensor 270. The sheet detection sensor 270 detects the conveyed sheet S. For example, in the case where the sheet detection sensor 270 detects the sheet S, the control unit 400 and the information processing unit 160 start the sheet measurement sequence. By starting the sheet measurement sequence, the control unit 400 and the information processing unit 160 cause the ultrasonic sensor 120 and the optical sensor 150 to perform the measurement operation.

[0064] The ultrasonic sensor 120 measures the sheet S by using ultrasonic waves, and outputs an output value of a predetermined voltage value as a measurement result. The information processing unit 160 acquires the output value of the ultrasonic sensor 120, and derives the transmittance of the sheet S from the output value given when the sheet S exists and the output value given when the sheet S does not exist. The information processing unit 160 detects information corresponding to the basis weight from the transmittance of the sheet S. The optical sensor 150 is, for example, a contact image sensor (CIS). The information processing unit 160 stores the brightness value of each pixel in the memory 1601 as a result of imaging obtained by the optical sensor 150. The information processing unit 160 converts the brightness value of each pixel stored in the memory 1601 into information corresponding to surface properties such as a cumulative difference value as the sum of differences in brightness values ​​of adjacent pixels and brightness.

[0065] The information processing unit 160 transmits the information corresponding to the basic weight and the information corresponding to the surface property to the control unit 400. The control unit 400 determines the type of the sheet S (paper type, paper type information) based on the acquired information corresponding to the basic weight and the information corresponding to the surface property. The control unit 400 determines one image forming condition (printing mode) corresponding to the type of the sheet S from a plurality of printing modes stored in the printing mode database 402. The control unit 400 displays information related to the determined printing mode on the display of the operation unit 502. The printing mode is an operation mode for controlling image formation under predetermined image forming conditions (e.g., secondary transfer bias value, target fixing temperature of the fixing device 201E, and conveying speed during fixing). The printing modes are named by sheet type, such as "thin paper sheet 1", "thin paper sheet 2", "plain paper sheet 1", "coated paper sheet 1", "coated paper sheet 2", and "coated paper sheet 3". The description given here relates to a method for determining image forming conditions based on the type of the sheet S, but the method is not limited thereto. For example, the control unit 400 determines the type (paper type, paper type information) of the sheet S based on the acquired information corresponding to the surface property. The control unit 400 can determine one image forming condition (printing mode) corresponding to the information corresponding to the type and basis weight of the sheet S from among a plurality of printing modes stored in the printing mode database 402.

[0066] <Media Sensor Configuration>

[0067] Figure 4 and Figure 5 2 is an explanatory diagram of the configuration of the media sensor 100 . Figure 4 This is a diagram of the media sensor 100 as viewed from a direction perpendicular to the conveyance direction of the sheet S. Figure 5 This is a diagram of the media sensor 100 viewed from the upstream side in the conveyance direction of the sheet S.

[0068] like Figure 4 As shown, the media sensor 100 is arranged between the conveying roller pair 280 and the conveying roller pair 290, and acquires information corresponding to the basis weight of the conveyed sheet S and information corresponding to the surface property of the conveyed sheet S. The sheet detection sensor 270 is arranged at a position substantially the same as that of the media sensor 100 in the conveying direction of the sheet S. It is sufficient that the sheet detection sensor 270 is disposed on the upstream side of the media sensor 100 in the conveying direction of the sheet S. The media sensor facing roller 260 is arranged at a position facing the media sensor 100 with respect to the conveying path of the sheet S. The media sensor facing roller 260 is configured to move in a direction toward the media sensor 100 and in a direction away from the media sensor 100.

[0069] like Figure 5 As shown, in the media sensor 100, the ultrasonic sensor 120 and the optical sensor 150 are arranged at the same position in the conveying direction of the sheet S and arranged side by side in the direction orthogonal to the conveying direction. The ultrasonic sensor 120 includes an ultrasonic transmitter 130 and an ultrasonic receiver 131. The optical sensor 150 is a CIS including a light source 1501 (e.g., LED) and a line sensor 1502 as a light transmitter and a light receiver, respectively. The optical sensor 150 can be configured by using a CCD image sensor or a CMOS image sensor.

[0070] The optical sensor 150 measures the brightness value of the received light. For this purpose, the sheet S needs to be kept at the optical focus position of the optical sensor 150. In the case where the ultrasonic sensor 120 measures the sheet S, the measurement accuracy is improved when no influence is generated due to the vibration of the conveyed sheet S. For this purpose, the sheet S needs to be conveyed in a stable posture.

[0071] In at least one embodiment, in order to convey the sheet S in a stable posture, a roller 260 facing the media sensor and a sheet pressing roller 261 are arranged between the conveying roller pair 280 and the conveying roller pair 290. The roller 260 facing the media sensor and the sheet pressing roller 261 are arranged at the same position in the conveying direction of the sheet S. The roller 260 facing the media sensor is arranged to face the optical sensor 150 across the conveying path, and is configured to press the optical sensor 150 toward the sheet S. As a result, when the media sensor 100 measures the surface of the sheet S, changes in the position and posture of the sheet S are reduced. Therefore, the media sensor 100 can measure characteristic quantities such as surface properties and basis weight of the sheet S in a stable state. The sheet pressing roller 261 is arranged at a position where the ultrasonic sensor 120 is clamped between the sheet pressing roller 261 and the roller 260 facing the media sensor.

[0072] <Measurement of Basis Weight>

[0073] In the ultrasonic sensor 120, an ultrasonic transmitter 130 and an ultrasonic receiver 131 are arranged at opposing positions across the conveying path. The ultrasonic transmitter 130 is arranged on the upper block 110 side of the media sensor 100. The ultrasonic receiver 131 is arranged on the lower block 109 side of the media sensor 100. The ultrasonic sensor 120 receives ultrasonic waves output from the ultrasonic transmitter 130 via the conveying path of the sheet S through the ultrasonic receiver 131. The ultrasonic receiver 131 outputs information (output value) for determining the basis weight of the sheet S based on the received ultrasonic waves.

[0074] The ultrasonic transmitter 130 and the ultrasonic receiver 131 are each formed of a piezoelectric element (also referred to as a "piezoelectric element"), which is an element for mutual conversion between mechanical displacement and electrical signals, and an electrode terminal. The ultrasonic transmitter 130 generates ultrasonic waves by oscillation of the piezoelectric element in response to input of a pulse voltage having a predetermined frequency to the electrode terminal. The generated ultrasonic wave propagates through the air. When the ultrasonic wave reaches the sheet S, the ultrasonic wave causes the sheet S to vibrate. The ultrasonic wave generated in the ultrasonic transmitter 130 propagates to the ultrasonic receiver 131 via the sheet S. The piezoelectric element of the ultrasonic receiver 131 causes the electrode terminal to generate an output voltage corresponding to the amplitude of the received ultrasonic wave. The output voltage has a voltage value corresponding to the basis weight of the sheet S. The output voltage is transmitted to the information processing unit 160 as an output value.

[0075] The ratio between the output voltage given when the sheet S is not present and the output voltage given when the sheet S is present between the ultrasonic transmitter 130 and the ultrasonic receiver 131 is the transmittance. The transmittance of ultrasonic waves varies depending on the basis weight (area density) of the sheet S. Therefore, the basis weight of the sheet S can be estimated by using a conversion formula or a conversion table between the transmittance and the basis weight.

[0076] <Measurement of surface properties>

[0077] The surface property of the sheet S is detected by using the optical sensor 150. Light emitted from the light source 1501 irradiates the sheet S at a constant angle through a light guide (not shown). The sheet S reflects the irradiated light. The light reflected by the sheet S forms an image on the line sensor 1502 via a lens (not shown). In this way, the line sensor 1502 can read the light reflected from the sheet S as an image. Fig. 6A and Figure 6B 2 is an explanatory diagram of a reading result obtained by the optical sensor 150 .

[0078] exist Fig. 6A , an example of an image read by the line sensor 1502 is shown. The line sensor 1502 includes a plurality of light receiving elements 1502a. The plurality of light receiving elements 1502a are arranged in a direction orthogonal to the conveying direction of the sheet S, so the line sensor 1502 can read an image corresponding to one line at a time. Fig. 6A In the example of , 400 light receiving elements 1502a are arranged, and thus the line sensor 1502 can read an image of 400 pixels (A1 to A400) at a time.

[0079] In at least one embodiment, a plurality of light receiving elements 1502a are arranged to achieve a resolution of 300 dpi. The image corresponding to one line read by the line sensor 1502 at one time is not sufficient as the amount of information for judging the surface properties of the sheet S. This is because, in the image corresponding to one line, there is a large deviation in the reading results of each reading position. For this reason, the optical sensor 150 performs multiple reading operations on the conveyed sheet S and obtains the reading results of the images of multiple lines of the sheet S. By connecting the reading results of the multiple lines in the conveying direction of the sheet S, the trend of the surface properties of the sheet S for a predetermined size can be judged.

[0080] The information processing unit 160 digitally processes the image read by the optical sensor 150, and stores the result of the digital processing as an output value (luminance value) of each pixel in the memory 1601. The information processing unit 160 obtains the cumulative difference, brightness, and peak-to-peak (PP) value of the luminance value from the luminance value of each pixel stored in the memory 1601, and stores these information in the memory 1601.

[0081] The cumulative difference value is a value obtained by summing the results of accumulating the differences in brightness values ​​of adjacent pixels of the image read by the line sensor 1502 for the number of lines. The cumulative difference value is an indicator of sheet unevenness. Figure 6B In , when the detection value of each pixel is represented by the pixel position (1 to n) and the detection line (A to N), the cumulative difference value Y is represented based on the following formula (1) by using the cumulative difference value "k" of each line. Figure 6B The detection pixel data direction of is the arrangement direction of the light receiving elements 1502a of the line sensor 1502 (the direction of pixels of one line). Figure 6B The detection line direction is the conveying direction of the sheet S.

[0082]

[0083] The brightness is the sum of the integrated values ​​of the luminance values ​​of the respective pixels received by the line sensor 1502 for the number of detection lines, and represents the brightness of the surface of the sheet S. The brightness M is represented by the following equation (2).

[0084] M=A1+A2+...+B1+B2+...+G1+G2+...+Nn... (2)

[0085] The PP value is a value obtained by summing the difference between the maximum and minimum values ​​of the brightness value of a line for the number of detection lines. A transparent film made of a resin such as PET reflects less light irradiated from the light source 1501 and is detected as having low brightness. For sheets such as embossed paper sheets having a surface with intentionally set geometric unevenness, the unevenness increases the brightness difference between adjacent pixels, resulting in a large cumulative difference. For recycled paper sheets, the brightness value is uneven in the fiber direction, and after several recycling processes, the pulp fibers become shorter, so the surface properties are often detected as rough. On the other hand, for coated paper sheets, the coating layer on the surface makes the paper sheet look less uneven, and the cumulative difference tends to be smaller. Brightness and PP values ​​are parameters used to distinguish these sheets.

[0086] The control unit 400 acquires the basic weight, cumulative difference, brightness, and PP value as feature quantities of the sheet S from the information processing unit 160, and determines the printing mode by referring to the printing mode database 402. The control unit 400 performs image formation corresponding to the print job by using image forming conditions based on the determined printing mode.

[0087] <Position Control of Roller Facing Media Sensor>

[0088] As described above, the media sensor facing roller 260 is configured to move in a direction toward the media sensor 100 (optical sensor 150) and in a direction away from the media sensor 100. That is, the media sensor facing roller 260 is movable between a first position separated from the optical sensor 150 and a second position closer to the optical sensor 150 than the first position. The media sensor facing roller 260 presses the sheet S toward the optical sensor 150 by moving to the second position. In a case where the media sensor facing roller 260 is in the second position, the sheet S is preferably pressed against the optical sensor 150. In this manner, the media sensor facing roller 260 is a rotating member serving as a pressing member that presses the sheet S toward the optical sensor 150. The same applies to the sheet pressing roller 261.

[0089] Figure 7 It is a layout diagram of a moving mechanism for moving the roller 260 facing the media sensor and the sheet pressing roller 261 . Figure 71 is a diagram viewed from above the roller 260 and the sheet pressing roller 261 facing the media sensor (the upper block 110 side of the roller 260 and the sheet pressing roller 261 facing the media sensor). The moving mechanism 700 includes a motor 300, a rotating shaft 301, a cam 302, a detection plate 303, a rotation detection sensor 304, a gear 305, and a mounting plate 306. The roller 260 and the sheet pressing roller 261 facing the media sensor are attached to the mounting plate 306. The ultrasonic transmitter 130 of the ultrasonic sensor 120 is not mounted to the mounting plate 306, but is fixed to the upper block 110 of the media sensor 100.

[0090] When the motor 300 is driven to rotate by the control unit 400, the gear 305 rotates. The rotation of the gear 305 causes the rotation shaft 301 to rotate. The rotation of the rotation shaft 301 causes the cam 302 and the detection plate 303 to rotate. The rotation of the cam 302 causes the mounting plate 306 to move up and down. As the mounting plate 306 moves up and down, the roller 260 facing the media sensor and the sheet pressing roller 261 move. As a result, the roller 260 facing the media sensor and the sheet pressing roller 261 move synchronously between the first position and the second position.

[0091] The positions of the roller 260 and the sheet pressing roller 261 facing the media sensor are detected by using the rotation detection sensor 304. The rotation detection sensor 304 is a photointerrupter. The rotation detection sensor 304 includes a light emitter and a light receiver arranged to face each other, and is configured so that the light receiver receives light output from the light emitter. The positions of the roller 260 and the sheet pressing roller 261 facing the media sensor are determined based on whether the light output from the light emitter is blocked by the detection plate 303. For example, the rotation detection sensor 304 outputs a detection signal of a first state when the light is not blocked, and outputs a detection signal of a second state different from the first state when the light is blocked.

[0092] Fig. 8A and Figure 8B 2 is an explanatory diagram of the operation of the moving mechanism 700. Here, a description is given of the operation of the moving mechanism 700 to move the roller 260 facing the media sensor, but the same operation applies to the sheet pressing roller 261. Fig. 8A and Figure 8B 300 is a diagram of the moving mechanism 700 as viewed from the detection plate 303 side (in a direction orthogonal to the conveying direction of the sheet S). The motor 300 and the gear 305 are not shown. Fig. 8A , a state in which the roller 260 facing the media sensor has moved to a first position separated from the optical sensor 150 is shown. Figure 8B , a state is shown in which the media sensor-facing roller 260 has moved to the second position in which the media sensor-facing roller 260 presses the sheet S against the optical sensor 150 .

[0093] The mounting plate 306 is configured to rotate around a rotation axis 306a. The mounting plate 306 is connected to a spring 307 and is urged by the spring 307 in a direction away from the optical sensor 150. The rotation angle of the mounting plate 306 changes according to the rotation position of the cam 302 and the spring 307. As the rotation angle of the mounting plate 306 changes, the position of the roller 260 facing the media sensor changes from the first position ( Fig. 8A ) and the second position ( Figure 8B )

[0094] The rotation position of the cam 302 can be determined based on whether the detection plate 303 mounted on the rotating shaft 301 blocks the light from the rotation detection sensor 304. As shown, the detection plate 303 has an array shape. In the case where the detection plate 303 rotates together with the rotating shaft 301, the detection signal output from the rotation detection sensor 304 changes. The rotation position of the cam 302 is detected based on the state of the detection signal. For example, in the case where the detection signal switches from the second state to the first state, the roller 260 facing the media sensor is in the first position ( Fig. 8A ), and in the case where the detection signal switches from the first state to the second state, the roller 260 facing the media sensor is in the second position ( Figure 8B ). By stopping the rotational drive of the motor 300 at each timing, the roller 260 facing the medium sensor stops at the first position or the second position.

[0095] Fig. 9 : is a configuration diagram of the media sensor facing roller 260. The media sensor facing roller 260 has a dumbbell shape, and a sponge material 2601 serving as a cleaning member is wound around the central portion of the media sensor facing roller 260. The media sensor facing roller 260 has two functions. Fig. 10A and Fig. 10B Each of them is an explanatory diagram of the function of the roller 260 facing the media sensor.

[0096] The first function of the roller 260 facing the media sensor is to maintain the distance ( Fig. 10A ). The roller 260 facing the media sensor maintains the distance between the sheet S and the light guide 1503 and suppresses positional variation (swing) of the sheet S by pressing the sheet S against the light guide 1503 of the optical sensor 150. Therefore, the optical sensor 150 can measure the sheet S in a state where the sheet S is stable. The second function of the roller 260 facing the media sensor is to wipe the surface of the light guide 1503 with the sponge material 2601 to remove paper dust (cleaning) by rotating after the sheet has passed. Fig. 10B). As described above, the light guide 1503 is used to illuminate the sheet S with light emitted from the light source 1501 at a fixed angle.

[0097] Fig.11 2 is a process flow chart for illustrating the movement process of the roller 260 facing the media sensor. This process is performed when the image forming apparatus 201 is started or returns from the sleep state to perform a print job. Note that when the movement of the roller 260 facing the media sensor is controlled, the movement of the sheet pressing roller 261 is also controlled in the same manner. FIG. 12A to FIG. 12C is an explanatory diagram of the operation of the roller 260 facing the media sensor during the moving process. Here, a description is given of a case where the control unit 400 performs the process, but the process may also be performed by the information processing unit 160 under the control of the control unit 400.

[0098] When the image forming apparatus 201 is started or returns from the sleep state, the control unit 400 rotationally drives the motor 300 to move the roller 260 facing the media sensor to the first position so as not to hinder the conveyance of the sheet S (step S111). This causes the roller 260 facing the media sensor to move away from the optical sensor 150 ( Fig. 8A ). In an operation mode in which the characteristic amount of the sheet S is not measured, the roller 260 facing the media sensor is maintained at the first position. In a media sensor mode for measuring the characteristic amount of the sheet S, the roller 260 facing the media sensor is movable between the first position and the second position.

[0099] In the case where the media sensor mode is set (step S112), the control unit 400 performs initial adjustment such as calibration of the optical sensor 150 (step S113). For example, an instruction for the media sensor mode may be given from the operation unit 502. When the initial adjustment starts, the control unit 400 rotationally drives the motor 300 to move the roller 260 facing the media sensor to the second position so as to abut against the optical sensor 150. After the initial adjustment ends, the control unit 400 rotationally drives the motor 300 to move the roller 260 facing the media sensor to the first position and away from the optical sensor 150.

[0100] In the initial adjustment, the media sensor 100 is activated, and in a state where a sheet does not exist, measurement is performed by the ultrasonic sensor 120. The measurement in a state where a sheet does not exist is a process for detecting an output change due to a change in the environment (e.g., temperature) by performing ultrasonic measurement in a state where the sheet S has not yet been conveyed. The measurement result in a state where a sheet does not exist is used to correct the environmental influence during the ultrasonic measurement. In addition, in the initial adjustment, black measurement of the optical sensor 150 is performed to detect a dark current. The light amount of the optical sensor 150 is adjusted based on the dark current. At this time, the roller facing the media sensor is in the second position, so the influence of external light is suppressed.

[0101] When the initial adjustment is completed, the control unit 400 waits until an instruction to start a print job is obtained. When the control unit 400 obtains an instruction to start a print job, the conveying unit 600 starts conveying the sheet S. When the sheet detection sensor 270 detects the sheet S after the sheet S starts to be conveyed, the control unit 400 stops conveying the sheet S by the conveying unit 600 (step S114). Fig. 12A , a state where the conveyance of the sheet S has stopped is shown. The sheet S reaches the measurement position of the media sensor 100, the leading end is conveyed to the conveyance roller pair 290, and the conveyance stops. The sheet S is in a state where a predetermined tension is applied to the sheet S by the conveyance roller pair 280 and the conveyance roller pair 290, and wrinkles on the surface are smoothed.

[0102] The control unit 400 that has stopped conveying the sheet S rotationally drives the motor 300 to move the roller 260 facing the media sensor to the second position and causes the sheet S to abut against the media sensor 100 (step S115). In this method, during conveying the sheet S to the measuring position of the media sensor 100, the roller 260 facing the media sensor is in the first position and thus does not hinder conveyance of the sheet S. Furthermore, during measurement of the sheet S by the media sensor 100, the roller 260 facing the media sensor presses the sheet S against the media sensor 100 at the second position to stabilize the posture of the sheet S.

[0103] The control unit 400, which has caused the roller 260 facing the media sensor to abut against the media sensor 100, confirms that the roller 260 facing the media sensor abuts against the media sensor 100 based on the detection result of the rotation detection sensor 304. For example, in a case where the detection signal output from the rotation detection sensor 304 has switched from the first state to the second state, the control unit 400 confirms that the roller 260 facing the media sensor (sheet S) abuts against the media sensor 100. After confirming that the roller 260 facing the media sensor (sheet S) abuts against the media sensor 100, the control unit 400 restarts the conveyance of the sheet S by the conveyance unit 600 ( Fig. 12B ).

[0104] While the conveyance of the sheet S is restarted, the control unit 400 performs a process of measuring the characteristic amount of the sheet S by the media sensor 100 (step S116). The media sensor 100 performs ultrasonic measurement by using the ultrasonic sensor 120, and derives the transmittance based on the measurement result. The control unit 400 derives the basic weight of the sheet S based on the transmittance by using a table or a mathematical formula representing the relationship between the transmittance and the basic weight. The media sensor 100 measures the surface property of the sheet S by using the optical sensor 150, and derives the cumulative difference and the brightness. The control unit 400 distinguishes the type of the sheet S based on the cumulative difference and the brightness. The control unit 400 refers to the print mode database to determine the print mode based on the basic weight and type of the sheet S, and sets the image forming conditions based on the determined print mode. When the measurement of the characteristic amount of the sheet S is finished, the control unit 400 stops the media sensor 100.

[0105] Then, the control unit 400 detects that the trailing end of the sheet S has passed the measurement position of the media sensor 100 based on the detection result of the sheet detection sensor 270 (step S117). Fig. 12C , a state in which the rear end of the sheet S has passed the measuring position of the media sensor 100 is shown. When the rear end of the sheet S passes the measuring position of the media sensor 100, the control unit 400 rotationally drives the motor 300 to move the roller 260 facing the media sensor to the first position (step S118). This causes the roller 260 facing the media sensor to move away from the optical sensor 150. That is, the control unit 400 moves the roller 260 facing the media sensor away from the optical sensor 150 after a predetermined period of time has passed since it was detected that the rear end of the sheet S has passed. As a result, the roller 260 facing the media sensor can clean the surface of the optical sensor 150 with the sponge material 2601 abutting against the surface of the optical sensor 150 for a predetermined period of time. Except when the feature amount of the sheet S is measured, the roller 260 facing the media sensor constantly stands by at the first position so as not to hinder the conveyance of the sheet S.

[0106] The roller 260 facing the media sensor may be moved to the second position and abut against the optical sensor 150 at times other than when the characteristic amount of the sheet S is measured. This is because, in a configuration in which the surface of the optical sensor 150 is cleaned by the roller 260 facing the media sensor only at the timing of measuring the characteristic amount of the sheet S, cleaning may not be performed for a long time. When the surface of the optical sensor 150 is not cleaned for a long time, the optical sensor 150 measures the characteristic amount of the sheet in a state where paper dust is attached to the surface, which results in a decrease in measurement accuracy. In order to prevent this, the roller 260 facing the media sensor moves to the second position at predetermined intervals to clean the surface of the optical sensor 150.

[0107] Fig.13 1 is a process flow chart for illustrating a process of cleaning the surface of the optical sensor 150 at predetermined intervals. Here, as an example, a case where the cleaning process is performed every time a predetermined number of sheets S are conveyed (every time an image is formed on a predetermined number of sheets). The predetermined interval is not limited thereto, and the cleaning process may be performed only when a predetermined period of time has passed since the previous cleaning process ended. Here, a case where the control unit 400 performs the cleaning process is described, but the cleaning process may be performed by the information processing unit 160 under the control of the control unit 400.

[0108] The roller 260 facing the media sensor stands by at the first position and is separated from the optical sensor 150. The control unit 400 counts the number of sheets S passing through and checks whether the count value has reached a specified number. In the case where the count value has reached the specified number (step S131), the control unit 400 waits until the sheet detection sensor 270 detects the sheet S. In the case where the sheet detection sensor 270 detects the sheet S (step S132), the control unit 400 rotationally drives the motor 300 to move the roller 260 facing the media sensor to the second position and to make the roller 260 facing the media sensor abut against the media sensor 100 (step S133).

[0109] The control unit 400 maintains the state in which the roller 260 facing the media sensor abuts against the media sensor 100 until after the sheet S passes through the measuring position of the media sensor 100, thereby removing paper dust from the optical sensor 150. The control unit 400 detects that the sheet S has passed through the measuring position of the media sensor 100 based on the detection result of the sheet detection sensor 270 (step S134). In the case where the sheet S passes through the measuring position of the media sensor 100, the control unit 400 rotationally drives the motor 300 to move the roller 260 facing the media sensor to the first position (step S135). As a result, the roller 260 facing the media sensor moves away from the optical sensor 150.

[0110] The above configuration of at least one embodiment (i.e., the configuration including the media sensor 100, the controller 200, the conveying unit 600, the roller 260 facing the media sensor, and the sheet pressing roller 261) becomes a sheet detection device. The sheet detection device can measure the characteristic quantities of the sheet S by using the media sensor 100, and determine the conveying conditions such as the conveying speed of the sheet S based on these characteristic quantities. During the conveying of the sheet S to the measuring position of the media sensor 100, the roller 260 facing the media sensor is separated from the media sensor 100 so as not to hinder the conveyance of the sheet S. As a result, the occurrence of conveying failures such as paper jams is suppressed. During the measurement of the sheet S by the media sensor 100, the roller 260 facing the media sensor moves toward the media sensor 100 and presses the sheet S against the media sensor 100. As a result, the swing of the sheet S during the measurement is suppressed, so the media sensor 100 can stably perform the measurement in a highly accurate manner.

[0111] The image forming apparatus 201 including at least one embodiment of such a sheet detection device can measure the feature quantities of the sheet S by using the media sensor 100, and determine the image forming condition of the sheet S based on the feature quantities. During the conveyance of the sheet S to the measurement position of the media sensor 100, the roller 260 facing the media sensor is separated from the media sensor 100 so as not to hinder the conveyance of the sheet S. During the measurement of the sheet S by the media sensor 100, the roller 260 facing the media sensor moves toward the media sensor 100 and presses the sheet S against the media sensor 100. As a result, the swing of the sheet S during the measurement is suppressed, and the media sensor 100 can stably perform the measurement. As a result, the reduction in the accuracy of sheet detection can be suppressed, and the occurrence of sheet conveyance failure can also be suppressed.

[0112] A description has been given above of the operation of the media sensor facing roller 260 relative to the optical sensor 150. The media sensor facing roller 260 is arranged to sandwich the ultrasonic sensor 120 between the media sensor facing roller 260 and the sheet pressing roller 261 (see Figure 5 ). With this configuration, when the sheet S reaches the measuring position of the media sensor 100, the roller 260 facing the media sensor and the sheet pressing roller 261 press the sheet S against the measuring position of the ultrasonic sensor 120. The ultrasonic sensor 120 transmits ultrasonic waves through the sheet S and measures the characteristic amount. The state of the sheet S is stabilized by the roller 260 facing the media sensor and the sheet pressing roller 261, so the characteristic amount of the sheet S can be accurately measured by the ultrasonic sensor 120.

[0113] Similarly, in the case of using a transmission optical sensor, the roller 260 facing the media sensor and the sheet pressing roller 261 are effective. Fig.141 is an explanatory diagram of the configuration of the media sensor using the transmission optical sensor 150t. The transmission optical sensor 150t transmits light through the sheet S and measures the characteristic amount. For this purpose, the light source 1501t and the line sensor 1502t are arranged to face each other across the conveying path. In addition, the roller 260 facing the media sensor is not included, and the sheet pressing roller 262 is arranged facing the sheet pressing roller 261 so as to clamp the optical sensor 150t. The state of the sheet S is stabilized by the sheet pressing roller 261 and the sheet pressing roller 262, so the characteristic amount of the sheet S can also be accurately measured by the transmission optical sensor 150t. In other words, the state of the sheet S is stabilized by the two rollers pressing the sheet S against the optical sensor 150 in addition to the roller 260 facing the media sensor directly pressing the sheet S against the optical sensor 150. As a result, the sheet S can be stably measured even by the transmission optical sensor 150t, the reduction in the accuracy of sheet detection can be suppressed, and the occurrence of sheet conveying failure can also be suppressed.

[0114] The above-described media sensor 100 is an example and is not limited to a configuration including the optical sensor 150 and the ultrasonic sensor 120 . The media sensor 100 may include other sensors capable of measuring characteristic quantities of the sheet S. Furthermore, the media sensor 100 may include any one of the optical sensor 150 and the ultrasonic sensor 120 .

[0115] Furthermore, in the above description, a configuration has been described in which the print mode database 402 is included in the memory 401 of the controller 200, but the storage location of the print mode database 402 is not limited thereto. For example, the print mode database 402 may be stored in the memory 1601 included in the media sensor 100. In this case, the information processing unit 160 determines the type and basis weight of the sheet S, and the information processing unit 160 also determines the print mode.

[0116] In the above description, the configuration of the image forming apparatus 201 has been described, but the present disclosure can be applied to any apparatus including a sheet detection device. For example, such a sheet detection device can be used in an image reading apparatus for reading an image printed on a sheet while conveying the sheet. The image reading apparatus includes an automatic document feeder (ADF). By incorporating a sheet detection device in the ADF, it is possible to stably read an image and convey a sheet.

[0117] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

[0118] This application claims the benefit of Japanese Patent Application No. 2023-149047, filed September 14, 2023, which is hereby incorporated by reference herein in its entirety.

Claims

1. A sheet detection device, comprising: A measuring component, used for measuring a characteristic quantity of the sheet conveyed by the conveying component; a pressing member movable between a first position separated from the measuring member and a second position closer to the measuring member than the first position; as well as a moving component configured to move the pressing member, wherein, when the sheet has not yet been conveyed by the conveying means to the measuring position of the measuring means, the pressing member is arranged at the first position by the moving means, wherein the moving means is configured to move the pressing member from the first position to the second position when the sheet has been conveyed by the conveying means to the measuring position of the measuring means, and The measuring unit is configured to measure the characteristic amount of the sheet in a state where the pressing member is arranged at the second position.

2. The sheet detection device according to claim 1, wherein: The moving unit is configured to move the pressing member from the second position to the first position after the conveying unit causes the leading end of the sheet in the conveying direction to pass through the measuring position.

3. A sheet detection device, comprising: A measuring component, used for measuring a characteristic quantity of the sheet conveyed by the conveying component; a pressing member movable between a first position separated from the measuring member and a second position closer to the measuring member than the first position; as well as a moving component configured to move the pressing member, wherein, when the sheet has not been conveyed by the conveying means to the measuring position of the measuring means, the pressing member is arranged at the first position by the moving means, and When the sheet has been conveyed by the conveying means to the measuring position of the measuring means, the pressing member moved by the moving means from the first position to the second position is arranged at the second position until the sheet passes the measuring position.

4. The sheet detection device according to claim 3, wherein: In a state where the pressing member is arranged at the second position, the pressing member is configured to abut against the sheet until the rear end of the sheet in the conveying direction passes the measuring position, and abut against the measuring component after the rear end of the sheet passes the measuring position.

5. The sheet detection device according to claim 1 or claim 3, further comprising: a sheet detection sensor configured to detect the sheet conveyed to the measurement position, The moving part is configured to move the pressing member from the first position to the second position when the sheet detection sensor detects the sheet.

6. The sheet detection device according to claim 5, wherein: The sheet detection sensor is arranged on the upstream side of the measuring member in the conveying direction of the sheet.

7. The sheet detection device according to claim 1 or claim 3, wherein: The moving means is configured to move the pressing member to the second position when performing an initial adjustment of the measuring means.

8. A sheet detection device, comprising: A measuring component, used for measuring a characteristic quantity of the sheet conveyed by the conveying component; a pressing member movable between a first position separated from the measuring member and a second position closer to the measuring member than the first position; as well as a moving component configured to move the pressing member, wherein the moving means is configured to move the pressing member from the first position to the second position when performing initial adjustment of the measuring means in a state where the sheet has not yet been conveyed to the measuring position of the measuring means, wherein the measuring component is configured to perform the initial adjustment in a state where the pressing member is arranged in the second position, and Wherein, the moving component is configured to move the pressing member from the second position to the first position after performing the initial adjustment.

9. The sheet detection device according to claim 8, in, After the initial adjustment is performed, the pressing member is arranged at the first position in a case where the sheet has not yet been conveyed by the conveying member to the measuring position of the measuring member, wherein the moving means is configured to move the pressing member from the first position to the second position when the sheet has been conveyed by the conveying means to the measuring position of the measuring means, and The measuring unit is configured to measure the characteristic amount of the sheet in a state where the pressing member is arranged at the second position.

10. The sheet detection device according to claim 8, wherein: In case the initial adjustment is performed, the pressing member is configured to move to the second position to abut against the measuring component.

11. The sheet detection device according to any one of claims 1, 3 and 8, wherein: The pressing member is a rotating member.

12. The sheet detection device according to any one of claims 1, 3 and 8, in, The pressing members are two rotating members, and The two rotating members are arranged such that the measurement position is located between the two rotating members in a direction orthogonal to a conveying direction of the sheet.

13. The sheet detection device according to any one of claims 1, 3 and 8, wherein: The moving part is configured to move the pressing member from the first position to the second position at predetermined intervals.

14. The sheet detection device according to claim 12, wherein: The pressing member includes a cleaning member, and is configured to clean the measuring member by causing the cleaning member to abut against the measuring member in the second position.

15. An image forming device comprising: The sheet detection device according to any one of claims 1 to 14; as well as An image forming means is configured to form an image by using an image forming condition based on the feature amount of the sheet measured by the measuring means.

Images